This invention relates to a new principle of incineration, a method for carrying out complete combustion of solid and liquid waste, and a furnace or a combustion plant utilizing the incineration principle.
The invention is suitable for the incineration and destruction of waste of any sort, solid or liquid and even so-called problem waste, such as plastic waste and waste from hospitals.
For combustion plants which do not work in association with specific gas cleaning units, which purify the flue gases before they are introduced into the atmosphere, it is important that the process of combustion proceeds under optimum conditions and that non-combustible particles, dust, ash, etc. are removed effectively within the combustion zone and are not carried out and emitted into the air together with the flue gases.
To keep air contaminations at a minimum, it is thus a main object with a combustion plant of this type to establish the highest possible complete combustion of the waste at the same time as all solid and non-combustible particles are separated, whereby essentially clean flue gases are emitted. It is common knowledge that satisfactory combustion cannot be obtained in only one combustion zone. Thus combustion in several combustion chambers is already utilized, where part of the combustion is conducted in a primary combustion zone and secondary combustion is conducted in subsequent combustion zones.
This combustion principle is for example used in the incinerator shown in Swiss Pat. No. 430018. The incinerator is equipped with a combustion chamber without grates and it has an inner wall of refractory material. By means of a vertical, perforated partition the furnace is divided into a primary combustion chamber and a secondary combustion chamber. Combustion air is led into the furnace from the outer walls of the furnace through a number of air jets situated at different heights and supplied with air from air tubes embedded in the brickwork of the furnace. Any necessary additional heat needed for combustion is provided by a burner which is situated outside the primary combustion chamber. Preferably a cyclone burner, placed at a distance above the bottom of the combustion chamber is utilized for this purpose.
However, this known equipment has several disadvantages. Firstly, a satisfactory degree of combustion will not be obtained with this construction. The secondary air from the air jets in the furnace walls is not satisfactorily mixed with the gaseous combustion products which move in layered streams into the secondary combustion chamber. Furthermore, the accompanying unburned solid particles will not be separated from the flue gases, whereby they are emitted into the air together with the flue gases.
To improve the degree of combustion an extra burner should also be provided in the secondary combustion chamber, and this is for example proposed according to the furnace construction described in Norwegian Pat. No. 125606. This will to a certain extent increase the efficiency of the secondary combustion, but still it will be unsatisfactory.
In performing practical combustion tests it has been experienced that the viscous, gaseous combustion products from the primary combustion hardly mix at all with the secondary combustion air. Thus, it is necessary to ensure a much stronger and more intense mixing effect, utilizing far greater mixing forces than has so far been generated within a combustion chamber.